In subsea hydrocarbon production systems, wellstream fluids are transported via pipeline back to a topsides production facility. Typically, flow assurance strategies are employed that prevent the formation of hydrates and prevent or mitigate the formation of wax deposits in the pipeline. For transportation of the hydrocarbons in subsea pipelines that are more than about 100 kilometers long, the currently available flow assurance strategies such as continuous injection of chemical inhibitors or pipeline heating can be impractical and uneconomic to implement.
An alternative strategy is to purposely cause the hydrates and wax to form subsea in such a manner that a flowable slurry is formed that does not block flow in the pipeline. This alternative strategy is known in the industry as “cold flow.” While efforts have demonstrated that sudden plugging may be avoided with cold flow, hydrate deposition in the form of a hydrate film on the pipe wall and mixer surfaces of a cold flow reactor can result in gradual constriction of the flow area and an unacceptable increase in pressure drop over extended periods of time. Conventional flow loop testing to date within the industry has not been able to assess this effect. However, recent efforts have shown this effect to be detrimental to the cold flow process.
Thus, it is desired to develop a technique to reduce or prevent hydrate and/or other solids deposition on the pipe walls thus improving the cold flow process.